This invention relates to timing devices and more particularly to a device for providing an adjustable dwell cyclic timing signal at a predetermined point in a cycle.
Many devices which are cyclic in nature require means for generating a cyclic control signal at a predetermined time in an operating cycle and having a predetermined dwell or duration. A common method for timing the operating cycle of machines, such as lathes, presses, etc., is through the use of cam actuated switches. A cam, which is rotated in synchronism with an operating cycle, opens and closes a switch at predetermined points in the cycle for generating timing signals. However, such an arrangement provides a very limited degree of flexibility. If the machine is to be modified for use in a different production sequence, the cam typically must be replaced to change the timing and dwell of the control signal. Flexibility is also limited by the fact that a separate cam and switch assembly is generally required for each different timing signal required in an operating cycle. Many processes may require perhaps one hundred or more separate control signals at different points in a cycle, with the signals having different durations. Considerable time and expense is required to replace or modify the cams when such processes are changed.